J Am Board Fam Pract: first published as 10.3122/jabfm.11.6.481 on 1 November 1998. Downloaded from 1 Unintentional Carbon Monoxide Poisoning From an I Unlikely Source Tim Struttmann, MSPH, Amy Scheerer, MSPH, T. Scott Prince, MD, and LindaA. Goldstein, phD Carbon monoxide poisoning is an occupational saws.6 In other industries, carbon monoxide poi­ health risk across a broad range of industries and sonings have been reported among workers using vocations (eg, firefighters, tollbooth operators, gasoline-powered pressure washers to clean ani­ miners, mechanics). In 1995 carbon monoxide mal housing on Iowa farms7 and among ~orkers poisoning was the cause of 42 occupational fatali­ using propane-powered floor burnishers in a Ver­ ties in the United States.1 In 1993,862 nonfatal mont pharmacy.8 cases of carbon monoxide poisoning resulted in This report documents an unusual case of car­ days away from work. The manufacturing and bon monoxide poisoning in that the incident oc­ retail trade industries accounted for the largest curred outdoors while a farmer was setting tobacco percentage of carbon monoxide poisonings (27.3 plants on a family farm. An extensive review of the percent and 24.2 percent, respectively); the agri­ literature found no cases of carbon monoxide poi- culture-forestry-fishing industry accounted for 3.1 . soning from tractor exhaust in an open field. percent.2 Although these values appear to repre­ sent carbon monoxide poisoning at work as a rare Case Report event, the percentages are highly conservative. InJune 1997 at approximately 1 PM, a 37-year-old The symptoms of carbon monoxide poisoning are female farmer (the victim), her husband, and nonspecific, and many nonfatal cases of carbon brother-in-law began planting tobacco in their monoxide exposure go undetected.3 It has been 4.5-acre field. The temperature exceeded 90 OF, estimated that one third of all carbon monoxide and the air was humid with little or no breeze. poisonings are undiagnosed.4 \Vhile the victim's husband drove the gasoline­ The most common sources of carbon monox­ powered tractor pulling the attached tobacco set­ ide are fire, vehicle exhaust, gasoline-powered en­ ter, the victim and her brother-in-law rode side­ gines (especially if operated in enclosed spaces), by-side on the setter (Figure 1). Seated with their http://www.jabfm.org/ and poorly ventilated or faulty furnaces and backs to the tractor, they were exposed to the back­ heaters.s Most work-related carbon monoxide ex­ ward venting of exhaust from the exhaust pipe un­ posures are caused by exhaust from poorly venti­ derneath the tractor. The victim was seated closest lated vehicles and by gasoline-powered machines to the exhaust pipe. operated in enclosed areas. Carbon monoxide poi­ By 4 PM, the victim and her brother-in-law re­ sonings among construction workers have in­ ported having headaches; the victim also com­ volved gasoline-powered washers in an under­ plained of dizziness and fatigue. Although her'· on 28 September 2021 by guest. Protected copyright. ground parking garage, gasoline-powered forklifts brother-in-law stopped working at 4:30 PM, the . in an enclosed warehouse, and gasoline-fueled victim insisted on finishing despite her increasingly severe headache, drowsiness, and dizziness. She began to miss setting plants, a task requiring hand­ Submitted 26] anuary 1998. PM From the Kentucky Injury Prevention and Research Cen­ eye coordination. At 6:30 she collapsed on the ter (TS, AS), and the Southeast Center for Agricultural tray of plants in front of her on the setter. Health and Injury Prevention (TS, TSP), and the Depart­ The victim's husband notified emergency med­ ment of Preventive Medicine and Environmental Health (TSP), University of Kentucky ~handler Medical Center, ical services at 7:30 PM, reporting that he thought Lexington; and the Center for InjUry Researc~ and Control his wife had carbon monoxide poisoning. At 7:42 (LAG), University of Pittsburgh. Address reprmt requests to Tim Struttmann, MSPH, Kentucky Injury Prevention and PM her blood pressure was 140/100 mmHg, heart Research Center, 333 'Valler Ave, Suite 202, Lexington, KY rate 96 beats per minute, and respiratory rate 20 40504-2915. This work was supported by the NIOSH Cooperative per minute. She complained of dizziness, light­ Agreement U06/CCU412957-01. headedness, headache, nausea, a pounding heart, Unintentional Carbon Monoxide Poisoning 481 J Am Board Fam Pract: first published as 10.3122/jabfm.11.6.481 on 1 November 1998. Downloaded from Figure 1. Tractor and setter. Distance from distal end of exhaust pipe to victim's seat on tobacco setter is approximately 48 inches. ted carbon monoxide at levels well above the ceiling limit of 200 ppm recommended by the National Institute for Occupa­ tional Safety and H ealth.9 These levels should not be ex­ ceeded a t any time. Discussion Carbon monoxide is an insi di­ ous occupational health hazard. and wheezing. At the hospital emergency depart­ T he gas accumulates quickly, even in well-venti­ ment, arterial blood gas measurements, an elec­ lated areas, and toxic effects ensue rapidly. Symp­ trocardiogram, a complete blood cell count, and a toms can manifest suddenly but are relatively non­ chemistry panel were ordered. She was treated specific (eg, headache, dizziness, weakness, with 100 percent oxygen through a nonrebreath­ nausea, visual disturbances, and confusion).5 Car­ ing mask and was given intravenous fluids. Al­ bon monoxide induces its toxic effects by binding buterol was administered by nebulizer because she to hemoglobin, with an affinity 240 times greater had a history of asthma. By the time blood was than oxygen, to form carboxyhemoglobin. The drawn for blood gas ana lysis, nearly 3 hours had net effect is a reduction in the oxygen-carrying ca­ elapsed since carbon monoxide exposure, and she pacity of the blood. had been on 100 percent oxygen for 36 minutes. The clinical signs and symptoms of carbon Her carboxyhemoglobin level was 23.3 percent; monoxide poisoning vary, but in general, symp­ hyperbaric oxygen treatment was not prescribed. tom severity correlates with carboxyhemoglobin All other tests were within normal limits. At 11 :OS level (Table 1). 5, 10,1 1 Symptom severity and car­ http://www.jabfm.org/ PM her carboxyhemoglobin level was 7.2 percent; boxyhemoglobin levels depend on (1) concentra­ she was discharged from the emergency depart­ tion of carbon monoxide in the environment, (2) ment at 12:10 AM. duration of carbon monoxide exposure, and (3) in­ Case follow-up included systematic carbon terval between exposure and clinical assessment. monoxide sampling of the tractor's exhaust sys­ Normal carboxyhemoglobin concentrations are 2 tem. A monitor was placed in the location where a percent or less for nonsmokers and 9 percent or on 28 September 2021 by guest. Protected copyright. worker would sit on the tobacco setter (about 48 less for smokers. 12 The victim reported having inches from the tractor's exhaust pipe; Figure 1) smoked four to five cigarettes on the day of the in­ while the tractor remained in a stationary position cident; she has a IS-year history of smoking a pack with the engin.e running. During a IS-minute pe­ of cigarettes a day. riod, the exhaust averaged 477 ppm of carbon Given the nonspecificity of.its symptoms, vic­ monoxide. Sampling was also conducted in condi­ tims can mistake carbon monoxide poisoning for tions that simulated planting procedures. The re­ the fiu, heat exhaustion, and food or pesticide poi­ sult was 384 ppm of carbon monoxide during a soning, among other similar ailments, and not 1S-minute period. seek medical treatment. For the same reason, Four additional gasoline-powered tractors with physicians frequently misdiagnose the condi­ the same exhaust configuration were tested; these tion.5,11 ,13 In this report, the victim and family tractors ranged from 29 to 34 horsepower and members had used the tractor-setter routinely, and were manufactured between 1947 and 1979. Re­ none reported symptoms of carbon monoxide poi ­ sults showed that three of the four tractors emit- soning. The victim's brother-in-law could have ex- 482 JABFP Nov.-Dec. 1998 Vol. 11 No.6 J Am Board Fam Pract: first published as 10.3122/jabfm.11.6.481 on 1 November 1998. Downloaded from perienced a mild case of carbon monoxide poison­ Table 1. Symptoms and Signs Associated With Various ing, though he reported having only a headache. Levels of Carbon Monoxide Poisoning. Although measuring carboxyhemoglobin lev­ Carboxy­ els is considered useful for determining the hemoglobin severity of exposure to carbon monoxide, there is Level Symptoms and Signs some debate regarding its reliability.!O,II,!4 Re­ 0% -10% None in healthy persons sults can be misleading in that they do not reflect 10% - 20% Headache, dyspnea on mild exertion severity of the initial exposure because of time 20% - 30% Throbbing headache, nausea or vomiting elapsed or treatment begun after the victim was (or both), t~ltigability and irritability, weak ness, difficulty concentrating removed from the carbon monoxide source.!O In 30% -40% Severe headache, dizziness, fatigue and this report, nearly 3 hours passed between the weakness, syncope on exertion, impaired exposure and her carboxyhemoglobin measure­ thought processes _ ment of 23.3 percent in the emergency depart­ 40% - 50% T.1chypnea, tachycardia, syncope, confusion 50% - 60% Respiratory failure, collapse, intermittent ment. By back-extrapolation, assuming an 80- convulsions or seizures, coma minute half-life for carbon monoxide in 100 60% -70% Respiratory failure, severe hypotension, percent oxygen and a 320-minute half-life in coma, frequently fatal , normal air, is a carboxyhemoglobin level of 41 >70% Coma, rapidly fatal I percent was estimated for the end of exposure ! Modified from Dolan,S 0150n,10 and llano and Raffin.